Upgrades?

Hey all, I have both the KWA KZ 75 as well as the KSC CZ 75 (I wanted to compare the two and everyone told me they were the same but one had "markings") While this isn't entirely true, it is for the most part, especially as far as upgrade compatibility would go.

My question is do you have any recommendations for upgrades to either of these guns. I dont' care if I have to go to KWA, KSC, or another third party. I've been disappointed to find that there does not seem to be any parts for these guns.

I've been contemplating high flow valves for the mags, because I'm pretty sure I've actually SEEN those before, but they're expensive, around $20 a valve! and I have 6 mags! This is still something I might do, but I've yet to find any reviews to say if they're worth it.

Other than that, I haven't been able to find anything, springs, inner barrel, outer barrel (chrome anyone?). I have upgraded to some walnut grips I got from CZ-USA, but that's all I've been able to do. So, I come here to see if any of you have had better luck.